The present invention relates generally to shock absorbers. More particularly, it relates to shock absorbers of the type which use both an elastomeric shear spring and flow of fluid through a restricted orifice for absorbing shock and dissipating energy.
Known shock absorbers of the type described include those disclosed in U.S. Pat. No. 2,818,249 issued Dec. 31, 1957 to Boschi, U.S. Pat. No. 3,658,314 issued Apr. 25, 1972, to Luzsicza, and, British Pat. No. 1,148,515 issued Apr. 16, 1969 to Moulton. In the British patent, a force transmitting member deforms a diaphragm for transmitting force through a fluid to an elastomeric shear spring. The fluid flows through an orifice covered by yieldable flaps which provide one-way flow. The Luzsicza device has a piston separating a gas pressure chamber from a fluid chamber and a bumper is mounted on the bottom of the outer member for limiting telescoping movement of the inner and outer members. It is necessary to machine the cylinder for the piston in order to provide good sealing and smooth piston movement. Maintaining effective seals on the piston over long periods of time is very difficult. The Boschi device includes a bladder in an inner chamber but there is no way to selectively charge the bladder with variable gas pressure. The bladder would also wear rapidly if the cylinder in which it moves is not smooth.